Purdue innovation could help people with severe hearing loss

May 14, 2013

Joshua Alexander, assistant
professor in Purdue University's Department of Speech, Language and Hearing
Sciences, tests hearing aids used by Mel Chua, Purdue doctoral candidate in
engineering education, in his laboratory. Alexander has created a computer
algorithm that could make it possible for hearing aids to help people with
severe hearing loss to hear high-frequency sounds such as "s,"
"sh," "f" and "th." (Purdue Research Foundation
photo)
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WEST LAFAYETTE, Ind. - Mel Chua, a Purdue
University doctoral candidate in engineering education, received her current
set of hearing aids in May 2012. She has severe hearing loss but has not worn
hearing aids most of her adult life because they did not offer a significant
improvement to her hearing.

"I got my first hearing aids before I
started kindergarten," she said. "I refused to wear them in fifth
grade, and I more or less went without them except for brief interludes at ages
16 and 20. I tried them at those times and decided they weren't helping
me."

Chua said hearing aids didn't help
her because she was still missing a lot of speech sounds, especially high-frequency
sounds, like "s" and "sh."

"When I competed in school and
district spelling bees in elementary and middle school, I had to ask if the
word I was supposed to spell was singular or plural," she said. "I
couldn't hear the high-frequency 's' sound at the end of words."

An innovation developed by a Purdue
researcher in the College of Health and Human Sciences may make it possible for people with severe hearing loss, like Chua, to hear
high-frequency sounds like "s," "sh," "f" and
"th."

"People with severe hearing loss have lost
the ability to hear certain pitches, and most commonly they're the highest
pitches," he said. "Current hearing aid technology works best for
people with some residual ability to hear these pitches, but there are too many
challenges for it to help listeners with a very restricted pitch range."

Alexander tested variants of existing hearing
aid technology, which use algorithms to move information from higher pitches
into a lower pitch range.

"Those who need this technology the most
are people like Mel. Unfortunately, because their pitch range is so limited,
everything is placed into a very narrow area which makes different speech
sounds too similar to one another. There is less to separate them," he
said. "Listeners have to relearn how to perceive a lot of information in
the new pitch range, assuming the sounds can be made different from one another
in the first place."

Rather than design an algorithm and hope that
listeners' perception would accommodate to it, Alexander discovered what
listeners needed to enhance perception in the new pitch range. He then designed
an algorithm to accommodate these perceptual needs.

"Unlike other algorithms that simply shift
high-frequency sounds to a lower pitch range, this algorithm mirrors and flips
them. By moving the highest pitched speech sounds, like 's,' to the lowest
pitches, the listener can more easily relearn them because they are still
different from other speech sounds in the mid-pitch range, like 'sh,' " he
said. "This also means the listener doesn't need to relearn the speech
sounds in the mid-pitch range because the algorithm hasn't displaced them as
far. Most of the change is at the extremities."

Alexander said the algorithm takes advantage of
other differences between speech sounds to enhance perception, and that
multiple features can be customized for each listener. It is meant to
complement existing hearing-aid technology rather than compete against it, and
it may even be used in conjunction with cochlear implants, which are surgically
implanted electronic devices.

"A new protocol is to give the person with
a cochlear implant a hearing aid, too. Implants give the high pitches that a
listener is missing, but not the low," he said. "The algorithm could
provide redundancy as the listener hears high pitches from both the implant and
the hearing aid."

Alexander spoke about his innovation during the
International Hearing Aid Conference in Lake Tahoe, Calif. He has received
funding from a National Institutes of Health Challenge Grant and Purdue's
Entrepreneurial Leadership Academy.

The next steps to develop the innovation include
finding partners to fully test the algorithm, place it in hearing aids and
validate it with additional testing.

The Purdue Office of Technology
Commercialization has filed a patent application on
Alexander's algorithm. For more information about developing and
commercializing this innovation, contact the Purdue Office of Technology
Commercialization at 765-588-3479, otcpatent@prf.org.

About Purdue Office of
Technology Commercialization

The Purdue Office of Technology
Commercialization operates one of the most
comprehensive technology-transfer programs among leading research universities
in the United States. Services provided by this office support the economic
development initiatives of Purdue University and benefit the university's
academic activities.